ye i'd combine the 3. if you want products focused exclusively on longer erections during lovemaking or whatever on docsprefer.com he gives a combination of products and explanation of what each product does.

you could start out with 1500IU vitamin E a day, 50 mg of zinc citrate a day and say 2/3 tablespoons of maca powder (can mix in yoghurt or something) and see what it does. give it a couple of weeks.

if that wont do anything you could try something more 'agressive' later on. or up the dose like stated in my first post

edit ye quintessent stated erection is due to a couple of factors low testosteron (mostly accompanied by too high estrogen). maca balances the hormones. next is neurotransmitters and nitric oxide. which is all quite well explained on dr.wongs sites also his audio podcast site by the way

zinc citrate is for providing nutrients to penis area and basically hormones testosteron and stuff.